From 0198cf8fdade326962b028f256ae4b9364fb1471 Mon Sep 17 00:00:00 2001
From: Krzysztof Rudnicki <krzysztofrudnicki0@gmail.com>
Date: Sun, 4 Jun 2023 13:53:20 +0200
Subject: [PATCH] feat: add code

---
 .gitignore              |  5 +++++
 .vscode/extensions.json |  5 +++++
 code/main.pl            | 40 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 .vscode/extensions.json
 create mode 100644 code/main.pl

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000..5e748880
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+*.swp
+.DS_Store
+bin/configlet
+bin/configlet.exe
+temp.pl
\ No newline at end of file
diff --git a/.vscode/extensions.json b/.vscode/extensions.json
new file mode 100644
index 00000000..82d7b92c
--- /dev/null
+++ b/.vscode/extensions.json
@@ -0,0 +1,5 @@
+{
+    "recommendations": [
+        "rebornix.prolog"
+    ]
+}
\ No newline at end of file
diff --git a/code/main.pl b/code/main.pl
new file mode 100644
index 00000000..3b899b2d
--- /dev/null
+++ b/code/main.pl
@@ -0,0 +1,40 @@
+% month_days(Month, DaysInMonth, DaysBeforeMonth) 
+% returns the number of days in Month and the number of days it takes to reach that date in year 2023
+% prolog works by defining facts and rules and when queried about them returns values
+% it works different from functional programming in this  aspect since it doesn't just follow instruction it returns output based on world state
+month_days('01', 31, 0).
+month_days('02', 28, 31).
+month_days('03', 31, 59).
+month_days('04', 30, 90).
+month_days('05', 31, 120).
+month_days('06', 30, 151).
+month_days('07', 31, 181).
+month_days('08', 31, 212).
+month_days('09', 30, 243).
+month_days('10', 31, 273).
+month_days('11', 30, 304).
+month_days('12', 31, 334).
+
+% day_of_year(Date, DayOfYear) converts a date to day of year number later used to calculate interval
+% It also checks if number of days given by user is smaller or equal to number of days in the given month and if no then it gives fail
+day_of_year(Date, DayOfYear) :-
+  atom_chars(Date, Chars),
+  append(DayChars, MonthChars, Chars),
+  atom_chars(Day, DayChars),
+  atom_chars(Month, MonthChars),
+  month_days(Month, DaysInMonth, MonthDays),
+  atom_number(Day, DayNumber),
+  (DayNumber > DaysInMonth -> fail ; DayOfYear is MonthDays + DayNumber).
+
+% interval(Date1, Date2) prints the number of days between Date1 and Date2
+% We always expect date to be in format ddmm where 'd' stands for day and 'm' stands for month
+% if the month or day is just a single digit we expecte there to be zero in front 
+% (like 0505 for 5th of may or 1105 for 11th of may or 0511 for 5th of november)
+% write(Interval) prints out result, nl writes newline to make output conform to project requirements as much as possible
+interval(Date1, Date2) :-
+  (day_of_year(Date1, DayOfYear1), day_of_year(Date2, DayOfYear2) ->
+    Interval is abs(DayOfYear2 - DayOfYear1),
+    write(Interval), nl
+  ;
+    write('Invalid input.'), nl, fail
+  ).
\ No newline at end of file